The subject invention relates to a document or similar item. More particularly, it relates to a document or similar item which has a high degree of security against tampering, and to methods and apparatus for producing and authenticating such documents.
U.S. Pat. No. 4,853,961; for: "Reliable Document Authentication System"; to: Pastor; issued: Aug. 1, 1989, discloses a system wherein a document is authenticated by encryption using a public key encryption system. The invention of the Pastor patent teaches authentication of a document by encryption of information derived from the document, incorporating that encrypted information into the document, recovering the encrypted information from the document and decrypting it, and comparing it to the information as originally included in the document.
While believed to be generally very effective for authenticating documents to detect alteration or tampering, the above described invention suffers from certain disadvantages with existing documents, or documents which are produced to an already defined format. For existing documents it is necessary to input information from the document to create the encrypted information. Typically, this would be done either by manual keyboard input or by some form of character recognition technology. Also, where documents are produced in large numbers to already defined format, e.g. driver's licenses, it is difficult to modify the format to provide for incorporation of the encrypted information in accordance with the Pastor patent.
Thus, it is object of the subject invention to provide a method and apparatus for producing a secure document, which are easily applied to existing documents or documents produced in a predefined format.